1. Field of the Invention
The present invention relates to a device for concentrating solar radiation. The concentration device of the invention enables solar radiation to be concentrated automatically towards a receiver.
2. Description of Related Art
Many techniques for producing solar energy use devices for concentrating solar radiation towards a receiver. Such devices make it possible to increase the irradiation of the receiver and to reduce its costs.
Such concentration devices use either concentration by reflection, by using a mirror, e.g. a parabolic mirror or a cylindro-parabolic mirror, or else concentration by refraction, e.g. by means of lenses. The receiver collects the solar energy, which is then used in the form of heat, e.g. for a thermodynamic power plant, or else in the form of light radiation, e.g. for a photovoltaic power plant. Some of such devices are steered relative to two axes, while others are steered relative to a single axis.
Generally, electric motors controlled by an electronic solar-tracking system are used to steer the device. On the basis of time of day and of the geographical position of a power plant, it is easy to define at any time the exact direction in which to point the concentration device. Often, a feedback mechanism is added that identifies the exact direction of the solar radiation relative to the direction in which the device is pointing, and that corrects the pointing of the device.
However, using electric motors suffers from drawbacks. In very large power plants, e.g. plants extending over several tens of hectares, the installation costs, and in particular the wiring costs are high. In small power plants, e.g. in power plants extending over several tens or several hundreds of square meters, the risks of a motor failing are high, and the power plant does not necessarily have a maintenance team present on site. In addition, electric motors require power that the power plant cannot supply directly. It must therefore be connected to the electricity supply grid not only as an electricity producer, but also as a consumer, or else it must be equipped with a battery.
Devices are also known that are arranged so that the solar radiation brings the receiver to the focal point of the concentrator, such as, for example, the device described in Document U.S. Pat. No. 4,476,854 that steers the concentrator by means of a fluid moving by evaporating.
However, such devices sometimes use equipment that is of limited reliability in the long term and that is of high cost.